Melt system including a melt unit with a side-loading hopper

ABSTRACT

A melt system that includes a melt unit. The melt unit includes a reservoir and a melter. The melter is configured to expose solid adhesive to a temperature sufficient to form a molten adhesive, which is deposited into the reservoir. The melt unit includes a hopper disposed above the melter and for holding a supply of the solid adhesive. The hopper has an access door disposed on a wall of the hopper that is movable between a closed position where the hopper is closed and an open position where an internal chamber of the hopper is accessible to receive the solid adhesive. The hopper and the solid adhesive in the hopper are thermally isolated from the reservoir.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.16/760,221, filed Apr. 29, 2020, which is a U.S. National StageApplication of PCT International Patent App. No. PCT/US2018/057715,filed Oct. 26, 2018, which claims the benefit of U.S. Provisional PatentApp. No. 62/579,349, filed Oct. 31, 2017, the entire disclosures of allof which are hereby incorporated by reference as if set forth in theirentireties herein.

TECHNICAL FIELD

The present disclosure relates to a melt system including a melt unitwith a thermal isolation region between the melt grid and a reservoir.

BACKGROUND

Conventional melt systems include a melt grid positioned below a hopper,a reservoir below the melt grid, a pump coupled to reservoir, and anapplicator coupled to the pump. The melt grid exposes the solid polymerstored in the hopper to an elevated temperature, which converts thepolymer into a molten liquid. The molten liquid is gravity fed to thereservoir where the pump transports the molten liquid to the applicator.The applicator deposits the molten liquid onto a substrate, such as anonwoven or other material. The top of the hopper has a filling lid thatcan be opened to add solid polymer to the hopper as needed.

Conventional melt systems have several drawbacks related to whenproduction is stopped and is later resumed. In operation, the moltenpolymer fills the reservoir and exits through the applicator as notedabove. Over time, however, in conventional melt systems, the melt gridconverts the polymer inside the hopper into a molten liquid. Here, themelt grid is effectively submerged within molten liquid. During aproduction stop, e.g., when a shift ends or a particular run iscomplete, the molten liquid inside the hopper (and melt grid) solidifiesinto a solid mass. To resume production, the temperature of the meltgrid is elevated, which elevates the temperature of the solid polymerwithin the melt grid and inside the hopper. Eventually the solid polymerinside the hopper is converted to a molten liquid and intendedthroughput from the applicator is realized. Thus, the restarting processrequires long start-up times that have a detrimental impact on the meltsystem efficiency.

Melt gain is another problem with conventional melt systems. Ininstances where the melt system is idling or product is stopped, meltgrid temperature can be decreased to stop polymer melting. However, heatretained by the molten liquid in the reservoir contributes heat to themelt grid thereby increasing the temperature of the melt grid. Theincreased melt grid temperature re-initiates polymer melting, which, inturn, increases the level of molten polymer in the reservoir. Theincrease temperature in melting causes the level of molten polymer inthe reservoir to rise. If melt gain is occurring when the melt system isshut down for an extended period, the molten polymer solidifies in thereservoir, the melt grid, and the hopper, creating a single mass ofsolid polymer. Restarting production takes longer because of the largesolid mass must be converted back to molten polymer before molten liquidcan be pumped to the applicator at the desired production rate.

Conventional melt systems also have drawbacks related to how the hoppersare used. First, typical melt systems do not provide a physical means,such as a window, to view the polymer level in the hopper withoutopening the filling lid. The filling lid must be kept closed at alltimes for safety reasons, except when filling the hopper. Thus,monitoring the solid polymer level in the hopper between loadinginstances is not practical. Polymer loading events are scheduled basedon several factors, including the system throughput, amount of polymeradded over a given period of time, and duration of machine productionruns. In addition, current hopper designs present safety risks tooperators when filling the hopper. When the filling lid is opened to addpolymer, the operator is exposed to the molten liquid, which is asignificant burn hazard. For certain applications, such as nonwovens,the polymer is loaded in the form of a bag or large sausage format. Thesize and weight of each bag (or sausage) can cause splashing of themolten liquid if thrown or dropped into the hopper, presenting anadditional burn hazard. Depending on the polymer type, noxious vaporsfrom outgassing may be encountered when the lid is opened. Furthermore,conventional melt systems have inherent space limitations due to thehopper design. Because the filling lid is located on top of the machine,existing hopper designs have an overall height limitation to ensureadequate operator access. In order to maximize hopper storage capacityin view of this height limitation, the overall machine footprint must beincreased. This can be a problem if the melt system is being installedin an existing manufacturing facility where space is limited.

SUMMARY

There is a need for melt system that can efficiently melt molten polymeron demand, address safety risks, provide a thermal isolation regionbetween reservoir holding molten polymer and the unmolten polymer in ahopper, increase storage capacity by directly storing only unmoltenmaterial in the hopper, and provide side loading access to the hopper.An embodiment of the present disclosure is a melt system configured toconvert a solid polymer material into a molten material. The melt unitincludes a reservoir, a melt grid disposed above the reservoir, athermal isolation region between the reservoir and the melt grid, and ahopper for storing unmolten polymer and having an access door and avisualization window.

The melt grid is configured to expose the solid polymer material to atemperature sufficient to form a molten polymer material and to depositthe molten material into the reservoir. The thermal isolation regionincludes an air gap in the upper portion of the reservoir below the meltgrid and/or an isolation chamber. The thermal isolation region thermallyisolates the hopper from molten polymer in the reservoir when moltenpolymer is in the reservoir. Thermal isolation minimizes heat transferfrom the molten liquid to the heated melt grid, which reduces melt gain.The hopper has a lower end, an upper end opposite the lower end, and awall that extends from the lower end to the upper end. The lower end canbe proximate to and open to the melt grid. The upper end and the walldefines an internal chamber that holds the supply of the solid polymermaterial. The hopper includes an access door disposed preferably on thewall including a visualization window. However, the access door may beon the upper end and the visualization window may be separate from theaccess door. The access door is movable between a closed position wherethe one hopper is closed and an open position where the internal chamberis accessible to receive the solid polymer material.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing summary, as well as the following detailed description ofillustrative embodiments of the present application, will be betterunderstood when read in conjunction with the appended drawings. For thepurposes of illustrating the present application, there is shown in thedrawings illustrative embodiments of the disclosure. It should beunderstood, however, that the application is not limited to the precisearrangements and instrumentalities shown.

FIG. 1 is a perspective view of a melt system according to an embodimentof the present disclosure;

FIG. 2 is a side elevation view of the melt system shown in FIG. 1; and

FIG. 3 is a cross-sectional view of a portion of the melt system takenalong line 3-3 in FIG. 1.

FIG. 4 is a cross-sectional view of the melt unit shown in FIG. 1 withthe other components of the melt system removed for clarity.

FIG. 5 is a perspective view of a melt system according to anotherembodiment of the present disclosure;

FIG. 6 is a cross-sectional view of a portion of the melt system takenalong line 6-6 in FIG. 5;

FIG. 7A is a cross-sectional view of the melt unit shown in FIG. 6 withthe other components of the melt system removed for clarity;

FIG. 7B is a cross-sectional view of a portion of the melt unit shown inFIG. 7A;

FIG. 7C is an exploded perspective cross-sectional view the melt unitshown in FIG. 7A; and

FIG. 8 is a schematic diagram of a control system for the melt systemdescribed herein.

DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS

Turning to FIGS. 1 and 2, an embodiment of the present disclosureincludes a melting system 10 configured to melt and deliver a liquid,such as a polymer material P, or more specifically a thermoplasticmaterial, downstream to dispensing equipment (not shown). The dispensingequipment can be used to apply the molten polymer material onto asubstrate. The substrate can be a nonwoven material used in hygiene orother applications such as paper and paperboard packaging or otherproduct assembly applications involving adhesives, or onto materialswhere application of a polymer material, such as an adhesive, is needed.The polymer material P can be a pressure sensitive adhesive. However, itshould be appreciated that melt system 10 can be adapted to processother polymer materials.

As shown in FIGS. 1 and 2, the melt system 10 generally includes a baseframe 12 mounted on wheels (not numbered), a control unit 14 supportedby one side of the base frame 12, and at least one melt unit. Inaccordance with the illustrated embodiment, the melt system 10 includesa plurality of melt units 20, 22 supported by the other side of the baseframe 12. The control unit 14 includes a cabinet that housescontrollers, displays, user interfaces, etc., an operator can use tocontrol operation of the melt system. The control unit 15 is connectedto the melt unit 20, 22 via wired connectors 16.

In accordance with the illustrated embodiment, the melt system 10includes a first melt unit 20 and a second melt unit 22. As illustrated,the first and second melt units 20 and 22 are substantially similar toeach other. For instance, the first melt unit 20 includes a first hopper60 and the second melt unit 22 includes a second hopper 61 that issimilar to the first hopper 60. Accordingly, only a single melt unit 20will be described below. It should be appreciated, however, that theremay differences between the first melt unit 20 and the second melt unit22. Specifically, the configuration of the access doors 80 a, 80 b andlocations of the visualization windows 90 a, 90 b between the first andsecond hoppers 60 and 61 can differ. For example, the first hopper 60may have at least one visualization window that is separate from theaccess door while the second hopper 61 has at least one access door thatinclude a visualization window. Furthermore, the melt system 10 mayinclude a single melt unit or it may include more than two melt units.The inventive principles as described herein can be scaled up or down insize depending on application requirements, such as for nonwovens orpackaging applications.

Continuing with FIGS. 1 and 2, the melt unit 20 is supported by the baseframe 12 and the underlying surface and extends upwardly along avertical direction 2. The melt unit 20 and control unit 14, and thus thebase frame 12, define the overall “footprint” of the melt system 10. Asillustrated, the footprint is substantially rectilinear and extendsalong a first lateral direction 4 and a second lateral direction 6 thatare perpendicular to each other and to the vertical direction 2. Thevertical direction 2, the first lateral direction 4, and the secondlateral direction 6 are directional components used to describe spatialrelationship of components and subcomponents of the melt system 10described below.

Continuing with FIGS. 1-3, the melt unit 20 includes a pump assembly 24proximate the base frame 12, a reservoir 30 coupled to the pump assembly24, one or more sensors 29 positioned in the reservoir 30, a melt grid40 above the reservoir 30, and a hopper 60 mounted above the melt grid40. The melt unit also includes a thermal isolation region 50 disposedbetween the reservoir 30 and the hopper 60. The melt system includes acontrol system 100 that controls operations of the melt unit 20, asshown in FIG. 8. The control system 100 includes a controller 102coupled to the one or more sensors 29 and the melt grid 40. The controlsystem 100 is used to control flow of molten polymer from the melt grid40 and into the reservoir 30 as explained below.

Referring to FIGS. 1-3, the thermal isolation region 50 creates abarrier between molten liquid M, typically a polymer material, in thereservoir 30 and the solid polymer material P in the hopper 60. Thethermal isolation region 50 helps maintain the temperature in the hopperbelow the melting temperature of the polymer material P. For example,the thermal isolation region 50 helps maintain the solid polymermaterial in the hopper 60 at a first temperature that is lower than asecond temperature of the molten polymer material in the reservoir 30 bycreating a thermal barrier that minimizes heat transfer from thereservoir 30 through the melt grid 40 to the hopper. As shown in FIG. 3,the thermal isolation region 50 comprises the gap G between the meltgrid 40 and the molten liquid M in reservoir. The thermal isolationregion 50 can be any space or structure that creates a thermal barrierto minimize or even eliminate thermal migration from the molten polymerin the reservoir to the solid polymer P in the hopper. For instance, thethermal isolation region 50 may be an upper portion of the reservoir 30,as shown in FIG. 3). In another embodiment, the thermal isolation regionmay comprise a separate component positioned between the reservoir 30and the melt grid 40, for example, a thermal isolation chamber 150 inFIG. 6). In some instances, there may be a thermal isolation region 50and/or separate component positioned between the hopper 60 and the meltgrid 40 (not shown).

Turning to FIGS. 3 and 4, the reservoir 30 captures the molten materialM exiting the melt grid 40. The reservoir 30 includes a base 32, a top34 opposite the base 32 along a vertical direction 2, and an outer wall36. The outer wall 36 includes four sides 37 a, 37 b, 37 c and 37 d (37a not shown). The outer wall 36 defines an inner surface 35 along whichthe sensor 29 is positioned. The base 32 has an inner surface 33, aportion of which is angled with respect to the vertical direction 2. Theinner surface 33 guides molten material M into a portal (not numbered)that feeds into pump assembly 24 below the reservoir 30. The amount ofmolten polymer M that accumulates in the reservoir 30 is based, in part,on a) the throughput of polymer through the melt grid 40, b) the outputof molten polymer from the reservoir 30, and c) the height of the outerwall 36.

In accordance with the illustrated embodiment, the thermal isolationregion 50 is disposed below the melt grid 40. As shown in FIGS. 3 and 4,the outer wall 36 has a height that is sufficient to facilitateformation of an air gap G between the melt grid 40 and a pool of moltenmaterial that accumulates at the base 32 of the reservoir 30 duringoperation. As shown, the thermal isolation region 50 comprises, at leastin part, the air gap G aligned with an upper portion 52 of the reservoir30. In this regard, it can be said the thermal isolation region 50includes the upper portion 52 of the reservoir 30. The upper portion 52of the outer wall 36 extends from the top 34 of the reservoir to an axisA that extends through the outer wall 36 of the reservoir 30. The axis Ais shown at a location above the base 32 of the reservoir. The extent ofgap G is selected to separate the bottom of the melt grid 40 from theheated, molten polymer M in the reservoir 30. The separation creates athermal barrier that can inhibit or minimize heat transfer from themolten liquid M to the melt grid 40.

Continuing with FIGS. 3 and 4, the melt grid 40 is configured to turnthe solid polymer material P in the hopper 60 into the molten polymermaterial M. The melt grid includes a bottom 42 and a top 44 spaced fromthe bottom 42 along the vertical direction 2. The bottom 42 of the meltgrid 40 is mounted to the top 34 of the reservoir 30. The hopper 60 iscoupled to the top 44 of the melt grid 40. The melt grid 40 has an outerwall 46 that includes four sides 47 a, 47 b, 47 c and 47 d (only 47 band 47 d are shown FIG. 4). The melt grid 40 may also include aplurality of parallel and spaced apart melting rails 48. The meltingrails 48 extend across the melt grid 40 along the second lateraldirection 6 (into the sheet in FIG. 3). The melting rails 48 definepassages 49 that extend between adjacent melting rails 48. The meltingrails 48 can have different orientations as needed. In some instances,cross-bars (not shown) may connect adjacent melting rails. Each meltingrail 48 includes one or more heater elements that elevate thetemperature of the melting rails 48 to the desired temperature forprocessing the polymer material P. The heating elements are connected tothe controller 102 via the wired connector 16. In addition, the meltgrid 40 may include guide members 43 coupled to the bottom the melt grid40. The guide members 43 guide polymer from exiting the from between themelting rails 48 into the molten polymer M. The guide members 43 mayreduce formation of air bubbles as the polymer falls from the bottom ofthe melt grid 40 into the reservoir 30.

The melt grid is designed for efficient heating to the desired operatingtemperature from a cooled state. In one example, the melt grid has amass selected to provide a watt density of 8-10 w/in³. Such a melt gridmay take about 20 minutes to reach its desired operating temperature. Inanother example, the melt grid has a mass selected to increase wattdensity and utilizes thin film heaters. In this example, the melt gridhas a watt density of 60-70 w/in³. Such a melt grid will take about 3-6minutes to reach its desired operating temperature. In contrast,conventional melt grids use heavy castings and cartridge heaters andhave a watt density of 4-5 w/in³. Conventional melt grids will takethirty or more minutes to reach the desired operating temperature.Accordingly, the melt grids as described herein may be considered lowmass melt grids and have a watt density is greater than 6-8 w/in³ andcould be as high as 60-70 w/in³. Such low mass melt grids heat up andcool down faster compared to the conventional melt grids. Faster heat-upand cooling increases operational efficiency by reducing the amount oftime the melt unit is not generating molten polymer waiting for thesystem to reach its desired operational temperatures.

Referring to FIGS. 3-4, the hopper 60 is configured to hold polymermaterial P. As illustrated, the hopper 60 has a lower end 62, an upperend 64 opposite the lower end 62 along the vertical direction 2, and awall 66 that extends from the lower end 62 to the upper end 64. Theupper end 64 includes an upper cover 68 that closes the upper end 64 ofthe hopper 60. The wall 66 extends around an entirety of the hopper 60such that the wall 66 and the upper cover 68 define an internal chamber65 that holds the polymer material P. The lower end 62 is substantiallyopen to the melt grid 40. As shown in FIGS. 3-4, the lower end 62 isopen to the melting rails 48 and passages 49 of the melt grid 40. Theupper cover 68 closes the top of the hopper and permits an increase inhopper height compared to conventional hoppers used in typical meltsystems. Because in the preferred embodiment, the hopper 60 isside-loading, as will be described below, the upper end 64 may beenclosed. This permits the hopper 60 to be designed and installed insuch a way that the upper end 64 extends closer to the ceiling than whatwould be possible with a typical top-loading hopper. This results inincreased polymer storage capacity over typical melt systems.

In accordance with the illustrated embodiment, the wall 66 includes aplurality of sides 72 a-72 d. As best shown in FIGS. 2 and 4, the wall66 includes a first side 72 a, a second side 72 b that intersects thefirst side 72 a, a third side 72 c that intersects the second side 72 band that is opposite the first side 72 a, and a fourth side 72 d thatintersects the first side 72 a (FIG. 2) and the third side 72 c. Thefourth side 72 d is opposite the second side 72 b. The first side 72 acan be considered the front side or front of the hopper 60 and the thirdside 72 c can be considered the back or back side of the hopper 60. A“side” of the hopper 60 can also be referred to as a side wall incertain embodiments. As shown, the upper cover 68 intersects all foursides 72 a-72 b. The four sides 72 a-72 d are arranged to form arectilinear cross-sectional shaped hopper. Although a rectilinearcross-sectional shaped hopper 60 is illustrated, the hopper 60 can haveother cross-sectional shapes. For example, in accordance with analternative embodiment, the hopper 60 has a tubular shape. In such anembodiment, the hopper 60 includes a wall 66 that forms a tubular shapedbody. In such an embodiment, the hopper 60 includes a single curvedwall.

As shown in FIGS. 1 and 2, with the preferred embodiment, the hopper 60is configured for side-access. The hopper 60 includes one or moreopenings 70 and one or more access doors 80 a, 80 b that are movablebetween a closed position and an open position to provide access to theinternal chamber 65. The hopper 60 may also include one or morevisualization windows 90 a, 90 b.

The side access doors 80 a, 80 b permit an operator to load polymermaterial P from the side of the hopper 60. In accordance with theillustrated embodiment shown in FIGS. 1 and 2, the hopper 60 includes afirst access door 80 a and a second access door 80 b that are positionedwith respect to each other along the vertical direction 2 and operableto cover the opening 70. When the access doors 80 a, 80 b are in theclosed position, the hopper 60 is closed. When the access doors 80 a, 80b are in the open position the internal chamber 65 is accessible toreceive the polymer material P from a location external to the hopper60. The operator opens the access door 80 a or 80 b and loads polymermaterial P into the internal chamber 65 when the supply falls below athreshold amount. The first and second access doors 80 a, 80 b thereforeallow side loading of polymer material P. When loading polymer materialP into the side of the hopper 60, both access doors 80 a, 80 b may beopened and a first stack of polymer material P created in the hopper 60.Then, the second access door 80 b can be closed to stabilize the pile ofpolymer material P, and loading of the hopper 60 can recommence withonly the first access door 80 a open until the hopper 60 is full. Asbest shown in FIGS. 1 and 2, first access door 80 a and the secondaccess door 80 b each pivot between the closed position and the openposition. In an alternative embodiment, however, the access doors 80 a,80 b are slidable between the closed position and the open position. Instill other embodiments, the melt grid may be used with hoppers that aretop loading and include a movable lid at the top of the hopper 60.

The visualization windows 90 a, 90 b includes a transparent panel thatpermits the operator to see inside the hopper 60 and observe the levelof polymer material P in the hopper 60. As illustrated, the first accessdoor 80 a and second access door 80 b includes a corresponding firstvisualization window 90 a and a second visualization window 90 b. Inalternative embodiments, however, the access doors 80 a, 80 b andvisualization windows 90 a, 90 b may be independent of each other. Forexample, the visualization window 90 a, 90 b can be disposed along oneof walls 66. If the level of polymer material P falls below a threshold,the hopper 60 can be reloaded with polymer material P as needed usingthe side access doors 80 a, 80 b. Reloading occurs without having toremove an upper cover as is required for conventional hopper designs.The side-loading hopper as described herein removes height limitationstypical in top-loading hoppers because use of the top filling lid iseliminated. Storage capacity is increased without increasing machinefootprint. Furthermore, the melt system 10 maintains solid polymermaterial in the hopper during operation, which reduces safety risks overtop-loading designs because there is no longer a molten pool in thehopper and the associated burn risks and noxious fumes. Furthermore, thevisualization windows 90 a, 90 b permit observation of the polymer levelat any time during operation of the melt system 10 without having toopen the hopper 60.

The melt units as described herein includes at least one side-loadinghopper, which allows an increase in height over conventional hoppers byeliminating the height limitation driven by the need for the operator toreach over the top of the hopper to reach the filling lid. This enablesincreased holding capacity in hopper, by as much as 20% to 30% or more,over conventional hoppers used in typical melting systems. Embodimentsof the present disclosure allow the operator to load material to ahigher level without being limited by lid and hopper ergonomics. Thevisualization windows, when included in the hopper, provide easyvisibility of the polymer level at all times from a distance inreal-time, which neither is included in nor is it easily achieved inconventional melt units. Furthermore, because the side-loadingfunctionality, during the filling process the operator is positioned soas to be effectively removed from direct exposure to fumes that might beemerging from the melt zone since he is not directly above the meltzone.

The hopper 60 has described and shown in figures disposed on top of themelt grid 40 that is separated from the molten material in the reservoir30 by the thermal isolation region 50 (or the air gap G). The thermalisolation region 50 inhibits heat transfer from the molten liquid to thesolid polymer stored in the hopper 60. However, the hopper 60 asdescribed herein can be used in melt systems with different types ofmelt grids and reservoir configurations than what is shown and describedabove. Rather, the hopper 60 can be used in any type of melt systemswhere molten material M and the solid polymer stored in the hopper 60are thermally isolated with respect to each other. In other words,embodiments of the present disclosure include a melt system thatincludes a hopper that is thermally isolated from the reservoir 30 thatcontains molten liquid.

Turning to FIG. 8, the control system 100 is used to control flow ofmolten polymer from the melt grid 40 and into the reservoir 30 asexplained below.

Referring to FIG. 3, in operation, the hopper 60 holds a supply of solidpolymer material P on top of the melt grid 40. The melt grid 40 hasheating elements that expose the solid polymer material P positionedabove the melt grid 40 to a temperature sufficient to form a moltenpolymer material M. The molten polymer material M flows through the meltgrid 40 and is deposited into the reservoir 30 and through one or morepassageways(not shown) to the pump assembly 24. The control system 100implements a closed-loop control mechanism to maintain adequate level ofmolten polymer M in the reservoir 30. The controller 102 receives asignal from the melt grid 40 with data concerning the melt gridtemperature. As polymer flows into the reservoir 30, the sensor 29determines the level of molten polymer in the reservoir. The sensor 29transmits a signal to the controller 102. The controller 102 determinesif the level of molten polymer M is at or higher than a threshold level.If the level of molten polymer M is at or higher than the thresholdlevel, the controller 102 causes the temperature of the melt grid 40 todecrease by a determined amount. The lower melt grid temperaturedecreases the rate of molten polymer M flowing into the reservoir 30.This results in the level of molten polymer M in the reservoirdecreasing as molten polymer M is pumped to the applicator (not shown).The sensor 29 detects when the level of molten polymer M falls below thethreshold level and transmits the signal to the controller 102. Thecontroller 102 causes the temperature of the melt grid 40 to increase,thereby increasing the amount of molten polymer P flowing into thereservoir 30. The feedback loop between sensor data and temperatureadjustment based on the sensor data controls the level of molten polymerM in the reservoir 30 to maintain an air gap below the melt grid 40.During the control process described above, the pump assembly 24,however, is used to continuously pump the molten material M from thereservoir 30 through hoses (not shown) to an applicator (not shown),which ejects the molten material M onto the desired substrate. As moltenmaterial M is ejected, the supply of polymer material P in the hopper 60is depleted. The supply of polymer material P may be observed throughthe visualization windows 90 a, 90 b (FIG. 2), when present, asdescribed above.

Another embodiment of a melt system is illustrated in FIGS. 5-7C. Themelt system 110 illustrated in FIGS. 5-7C is similar to the melt system10 shown in FIGS. 1-5. The melt system 10 and melt system 110 includecommon features and have similar modes of operation.

Turning to FIGS. 5-6, the melting system 110 is configured to melt anddeliver polymer material P downstream to dispensing equipment (notshown). The melt system 110 includes a base frame 112 mounted on wheels(not numbered), a control unit 114, and at least one melt unit 120. Thecontrol unit 114 includes a cabinet that houses controllers, displays,user interfaces, etc., an operator can use to control operation of themelt system 110. In accordance with the illustrated embodiment, the meltsystem 110 includes at least one melt unit 120. While only a single meltunit 120 is shown, the melt system 110 can include a plurality of meltunits. As shown in FIGS. 5-6, the melt unit 120 is supported by the baseframe 112 and the underlying surface and extends upwardly along avertical direction 2. The melt unit 120 and control unit 114, and thusthe base frame 112, define the overall footprint of the melt system 110.

Continuing with FIGS. 5 and 6, the melt unit 120 includes a pumpassembly 124 proximate the base frame 112, a reservoir 130 coupled tothe pump assembly 124, one or more sensors 29 (FIG. 6) positioned in thereservoir 130, a thermal isolation region 150, a melt grid 140 above thereservoir 130, and at least one hopper 160 mounted above the melt grid140, the reservoir 130 captures the molten material M exiting the meltgrid 140. A guide member 170 (FIG. 6) is positioned within the reservoir130. The guide member 170 is configured to guide molten polymer M to apool of molten liquid in the lower portion of the reservoir. The guidemember 170 is typically partially submerged in molten polymer M duringoperation of the melt system 110 as will be described further below. Themelt unit 120 also includes a control system 200 is used to control flowof molten polymer from the melt grid 140 and into the reservoir 130. Thecontrol system 100 for melt unit 120 operates in the same way to controlthe flow of molten polymer. The control system 100 includes a controller102 coupled to the one or more sensors 129 and at least the melt grid140.

Turning to FIGS. 7A-7C, the reservoir 130 captures the molten material Mexiting the melt grid 140. The reservoir 130 includes a base 132, a top134 opposite the base 132 along a vertical direction 2, and an outerwall 136. The outer wall 136 includes four sides 137 a, 137 b, 137 c and137 d (137 d not shown). The outer wall 136 defines an inner surface 135along which the sensor 129 may be positioned. As best shown in FIG. 7C,the interior of the base 132 has an inner surface 131 and a plurality offins 133 spaced apart with respect to each other along the secondlateral direction 6. The surface 131 feeds into a flow channel 139. Thesurface 131 and fins 133 guide the molten polymer M to the flow channel139. The flow channel 139 is open to the pump assembly 124 and guidesmolten material M into the pump assembly 124 below the reservoir 130. Aswill be explained further below, the amount of molten polymer M thataccumulates in the reservoir 130 is based, in part, on a) the throughputof polymer through the melt grid 140, b) the output of molten polymerfrom the reservoir 130, and c) the height of the reservoir 130.

Continuing with FIGS. 7A-7C, and in accordance with the illustratedembodiment, a thermal isolation chamber 150 is disposed below the meltgrid 40. The thermal isolation region 150 comprises the upper portion ofthe reservoir as described above an illustrated in FIGS. 1-4. Thethermal isolation chamber 150 creates an additional barrier betweenmolten liquid in the reservoir 130 and the solid polymer material P inthe hopper 160. The thermal isolation chamber 150 functions such thatmelt unit 120 can maintain the solid polymer material P in the hopper160 at a first temperature that is lower than a second temperature ofthe molten polymer material M in the reservoir 130. As described above,the thermal isolation chamber 150 can be any space or structure thatcreates a thermal barrier to minimize thermal migration from the moltenpolymer in the reservoir to the solid polymer P in the hopper. Thethermal isolation chamber 150 can define, at least in part, a gap Gbetween the melt grid 40 and the molten liquid M, as shown in FIG. 6,and the thermal isolation chamber 150.

Continuing in with FIGS. 7A-7C, the thermal isolation chamber 150 may bepositioned between the melt grid 140 and the reservoir 130. As shown,the thermal isolation chamber 150 includes an upper end 153, a lowerwall 154, an outer wall 156 coupled to the lower wall 154, and an outlet155 in the lower wall 154. The thermal isolation chamber 150 alsoincludes a guide path 159 that is aligned with and proximate to theoutlet 155. The guide path 159 extends between the discharge slot 145and the outlet 155. The lower wall 154, outer wall 156 and bottom 142 ofmelt grid 140 together define an internal air cavity C. The thermalisolation chamber 150 also includes a plurality of vent holes 158disposed along the outer wall 156. The vent holes 158 permit air toenter the internal cavity C and allow heat emanating from the moltenpool in the reservoir to escape. Air external to the melt unit 120 canenter the vent holes 158 to regulate temperature within the air cavityC. The air cavity C thus serves as a thermal barrier between the meltgrid 140 and reservoir 130, which in turn, helps maintain desiredtemperatures above melt grid 140, to maintain a solid polymer within thehopper, and below the thermal isolation chamber 150, to maintain moltenliquid M. During a product stoppage, the melt grid 140 can be maintainedat a temperature just below the melting temperature of the polymer toinhibit flow of the polymer in the reservoir 130. Furthermore, thereservoir can be temperature controlled to maintain the polymer withinthe reservoir in liquid form. Production can resume quickly by elevatingthe temperature of the melt grid 140, which initiates flow of thepolymer into the reservoir 130.

Continuing with FIGS. 7A-7C, the melt grid 140 is configured to turn thesolid polymer material P in the hopper 160 into the molten polymermaterial M. The melt grid includes a bottom 142 and a top 144 spacedfrom the bottom 142. The hopper 160 is coupled to the top 144 of themelt grid 140. The melt grid 140 has an outer wall 146 that includesfour sides 147 a, 147 b, 147 c and 147 d (147 d are not shown). The meltgrid 140 may also include a plurality of parallel and spaced apartmelting rails 148. The melting rails 148 extend across the melt grid 140along the lateral direction 4. The melting rails 148 define passages 149that extend between adjacent melting rails 48. Each melting rail 148includes heating elements that elevates the temperature of the meltingrails 148 to the desired temperature for the polymer material P beingprocessed by the melt unit 20. The heating elements may be controlled bythe control system.

As has been shown in FIG. 7B, the bottom 142 of the melt grid includes aplate 143 that guides polymer into the reservoir 130 to help preventand/or minimize formation of air bubbles in the polymer flow. The plate143 is angled toward its center to define a discharge slot 145. Thedischarge slot 145 is aligned with the guide path 159 and the guidemember 170. As illustrated, the plate 143 as a V-shaped cross-sectionalshape along a direction into the sheet of FIG. 7B. The plate 143 asshown conforms generally to the bottom of the each melting rail 148.Alternatively, the plate 143 can have other cross-sectional shapesand/or surface features that can be used to guide molten polymer towardthe discharge slot 145. The plate 143 is shown is mounted to the outerportion of the top of the thermal isolation chamber 150. Each meltingrail 148 is spaced apart from the plate 143 in order to create space formolten polymer M to pass through toward the discharge slot 145 of theplate 143 and into the guide path 159.

As illustrated in FIG. 7B, a guide member 170 is positioned in thereservoir 130 to receive molten polymer M from the melt grid 140. Theguide member 170 includes a guide member body 172 that has a base 174, atop 176, and angled side walls 178 a and 178 b. The guide member 170 canbe coupled to frame 171 (FIG. 7C), which is coupled to the reservoir130. The guide member body 172 has a height H that extends from the base174 to the top 176. The height is selected so that top 176 extends into,e.g. penetrates, the guide path 159 of the thermal isolation chamber150. As shown, the top 176 is generally aligned along the verticaldirection 2 with the outlet 155 of the thermal isolation chamber 150.The guide member 170 receives the molten material M and guides it intothe pool of molten material in reservoir 130 below (FIG. 6). The guidemember 170 can help minimize aeration and creation of air pockets in themolten material M as it exits the melt grid 140 and is collected in thereservoir 130.

Referring to FIGS. 6-7A, the hopper 160 is configured to hold polymermaterial P. As illustrated, the hopper 160 has a lower end 162, an upperend 164 opposite the lower end 162, and a wall 166 that extends from thelower end 162 to the upper end 164. The wall 166 includes four sides 169a, 169 b, 169 c and 169 d (169 d is not shown). Side 169 a can bereferred to as the front side or front of the hopper 160 and side 169 ccan be referred to as the back side or back of the hopper 160. Inaccordance with the illustrated embodiment, the sides 169 a-169 d arearranged to form a rectilinear cross-sectional shaped hopper. Inaccordance with an alternative embodiment, however, the hopper has atubular shape and includes a wall 166 that defines a tubular shapedbody. In such an embodiment, the hopper 160 includes a single curvedwall. The upper end 164 includes an upper cover 168 that closes theupper end 164 of the hopper 160. The wall 166 and the upper cover 168define an internal chamber 165 that holds the polymer material P.Because the hopper 160 may be side-loading as further describe below,the upper end 164 may be enclosed. This permits the hopper 160 to beinstalled in such a way that the upper end 164 extends closer to theceiling than what would be possible with a typical top-loading hoppers.This results in increased polymer storage capacity over typical meltsystems.

Referring to back to FIGS. 5 and 6, the hopper 160 has is configured toprovide side access to the internal chamber 165. This is possible due inpart to a “thermal valve” within the melt unit 120 created by completeengagement between the melt grid 140 and the semi-molten material. Aspolymers are suboptimal conductors of heat, the semi-molten material canblock upward migration of heat from the melt grid 140 to the hopper 160.As shown, the hopper 160 includes one or more side access doors 180 a,180 b that are configured to cover one or more access openings 70 (seeFIG. 5). The side access doors 180 a, 180 b permit an operator to loadpolymer material P from the side of the hopper 160 instead of from thetop. The side access doors 180 a, 180 b are substantially similar to theside access doors 80 a, 80 b described above. Thus, the one or moreaccess doors 180 a, 180 b are movable between a closed position and anopen position to provide access to the internal chamber 165. The hopper160 may be configured to allow visualization of the polymer held in thehopper 160. As shown, the hopper 160 may also include one or morevisualization windows 190 a, 190 b. The visualization windows 190 a, 190b permit the operator to see inside the hopper 160 and observe the levelof polymer material P in the hopper 160. The visualization windows 190a, 190 b are substantially similar to the visualization windows 90 a and90 b described above.

The hopper 160 has described and shown in FIGS. 5 and 6 is disposed ontop of the melt grid 140 that is separated from the molten material inthe reservoir 130 by the thermal isolation region 150. However, thehopper 160 as described herein can be used in melt systems withdifferent types of melt grids and reservoir configurations than what isshown and described above.

Referring to FIGS. 6 and 7A, in operation is the same as the melt unit20 and hopper described above. Specifically, the hopper 160 holds asupply of solid polymer material P on top of the melt grid 140. Theheating cartridge in the melt grid 140 exposes the solid polymermaterial P positioned above the melt grid 140 to a temperaturesufficient to form a molten polymer material M. The molten polymermaterial M flows through the melt grid 140 along the guide members 43and is deposited into the plate 143. The molten polymer material M flowsthrough the discharge slot 145 onto the guide member 170 and into thereservoir 130 to the pump assembly 124. The sensor 129 can determine thelevel of molten polymer M in the reservoir 130. The sensor 129 (onesensor is shown but more could be used) is communicatively coupled tothe melt grid via the control system 100, 200 (FIG. 8). As the level ofmolten polymer M in the reservoir 130 decreases (as determined by thesensor 129), the control system 100, 200 causes the temperature of themelt grid 140 to increase to a desired temperature. This, in turn,increases the rate at which polymer is exiting the melt grid 140. If thelevel of molten polymer M in the reservoir 130 approaches a thresholdlevel, the control system 100, 200 causes a decrease in the temperatureof the melt grid 140. This, in turn, decreases the rate at which polymerexits the melt grid 140. The pump assembly 124 may continuously pump themolten material M from the reservoir 130 to the dispensing device (notshown). As molten material M is ejected, the supply of polymer materialP in the hopper 160 is depleted. The supply of polymer material P may beobserved through the visualization windows 190 a, 90 b (FIG. 2), whenpresent, as described above.

While the disclosure is described herein using a limited number ofembodiments, these specific embodiments are not intended to limit thescope of the disclosure as otherwise described and claimed herein. Theprecise arrangement of various elements and order of the steps ofarticles and methods described herein are not to be considered limiting.For instance, although the steps of the methods are described withreference to sequential series of reference signs and progression of theblocks in the figures, the method can be implemented in a particularorder as desired.

What is claimed is:
 1. A melt system configured to convert a solidadhesive into a molten adhesive, the melt system comprising: at leastone melt unit having: a heated reservoir; a melter configured to exposesaid solid adhesive to a temperature sufficient to form a moltenadhesive, which is deposited into said heated reservoir; and a hopperdisposed above said melter and configured to hold a supply of the solidadhesive, said hopper having a lower end, an upper end opposite saidlower end, and a wall that extends from said lower end to said upperend, said lower end being proximate to and open to said melter, saidupper end and said wall defining an internal chamber that holds saidsupply of said solid adhesive, said hopper further having an access doordisposed on said wall, said access door movable between a closedposition where said hopper is closed and an open position where saidinternal chamber is accessible to receive said solid adhesive, whereinsaid hopper and said solid adhesive in said hopper are thermallyisolated from said heated reservoir.
 2. The melt system of claim 1,wherein the melter is positioned above said heated reservoir.
 3. Themelt system of claim 1, wherein said hopper includes an upper cover thatencloses the upper end of said hopper.
 4. The melt system of claim 1,wherein said hopper includes a visualization window configured to allowvisualization of a level of said solid adhesive inside said internalchamber.
 5. The melt system of claim 4, wherein said visualizationwindow includes a transparent panel to allow visualization of said levelof said solid adhesive inside said internal chamber.
 6. The melt systemof claim 4, wherein said access door includes said visualization window.7. The melt system of claim 4, wherein said visualization window isseparate from said access door.
 8. The melt system of claim 4, whereinsaid visualization window is disposed on said wall.
 9. The melt systemof claim 4, wherein said wall includes a first wall and a second wall,said access door disposed on said first wall and said visualizationwindow disposed on said second wall.
 10. The melt system of claim 9,wherein said first wall intersects said second wall.
 11. The melt systemof claim 1, wherein said hopper includes a first hopper and a secondhopper, said first hopper having a visualization window separate fromsaid access door thereof and said second hopper having an access doorincluding a visualization window.
 12. The melt system of claim 1,wherein said access door includes a first access door and a secondaccess door.
 13. The melt system of claim 12, wherein an opening isdefined in said wall of said hopper, said first access door and saidsecond access door collectively covering said opening in said closedposition.
 14. The melt system of claim 12, wherein said first accessdoor and said second access door are positioned with respect to eachother along a vertical direction.
 15. The melt system of claim 14,wherein said first access door and said second access door areindependently movable between said closed position and said openposition.
 16. The melt system of claim 1, wherein said access door ispivotable relative to said hopper between said closed position and saidopen position.
 17. The melt system of claim 1, wherein said wallincludes a plurality of walls arranged such that said hopper has arectilinear cross-sectional shape.
 18. The melt system of claim 1,wherein said wall is a curved wall such that said hopper has a tubularshape.
 19. The melt system of claim 1, wherein said access door isslidable between said closed position and said open position.
 20. Themelt system of claim 1, wherein the upper end of said hopper isenclosed.